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2024-02-20 ea08eeccae9297f7aabd2ef7f0c2517ac4549acc 
 kernel/kernel/notifier.c
....@@ -1,3 +1,4 @@
1
+// SPDX-License-Identifier: GPL-2.0-only
12 #include <linux/kdebug.h>
23 #include <linux/kprobes.h>
34 #include <linux/export.h>
....@@ -22,21 +23,10 @@
2223 		struct notifier_block *n)
2324 {
2425 	while ((*nl) != NULL) {
25
-		if (n->priority > (*nl)->priority)
26
-			break;
27
-		nl = &((*nl)->next);
28
-	}
29
-	n->next = *nl;
30
-	rcu_assign_pointer(*nl, n);
31
-	return 0;
32
-}
33
-
34
-static int notifier_chain_cond_register(struct notifier_block **nl,
35
-		struct notifier_block *n)
36
-{
37
-	while ((*nl) != NULL) {
38
-		if ((*nl) == n)
26
+		if (unlikely((*nl) == n)) {
27
+			WARN(1, "double register detected");
3928 			return 0;
29
+		}
4030 		if (n->priority > (*nl)->priority)
4131 			break;
4232 		nl = &((*nl)->next);
....@@ -104,6 +94,34 @@
10494 }
10595 NOKPROBE_SYMBOL(notifier_call_chain);
10696 
97
+/**
98
+ * notifier_call_chain_robust - Inform the registered notifiers about an event
99
+ *                              and rollback on error.
100
+ * @nl:		Pointer to head of the blocking notifier chain
101
+ * @val_up:	Value passed unmodified to the notifier function
102
+ * @val_down:	Value passed unmodified to the notifier function when recovering
103
+ *              from an error on @val_up
104
+ * @v		Pointer passed unmodified to the notifier function
105
+ *
106
+ * NOTE:	It is important the @nl chain doesn't change between the two
107
+ *		invocations of notifier_call_chain() such that we visit the
108
+ *		exact same notifier callbacks; this rules out any RCU usage.
109
+ *
110
+ * Returns:	the return value of the @val_up call.
111
+ */
112
+static int notifier_call_chain_robust(struct notifier_block **nl,
113
+				     unsigned long val_up, unsigned long val_down,
114
+				     void *v)
115
+{
116
+	int ret, nr = 0;
117
+
118
+	ret = notifier_call_chain(nl, val_up, v, -1, &nr);
119
+	if (ret & NOTIFY_STOP_MASK)
120
+		notifier_call_chain(nl, val_down, v, nr-1, NULL);
121
+
122
+	return ret;
123
+}
124
+
107125 /*
108126  *	Atomic notifier chain routines.  Registration and unregistration
109127  *	use a spinlock, and call_chain is synchronized by RCU (no locks).
....@@ -154,13 +172,30 @@
154172 }
155173 EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
156174 
175
+int atomic_notifier_call_chain_robust(struct atomic_notifier_head *nh,
176
+		unsigned long val_up, unsigned long val_down, void *v)
177
+{
178
+	unsigned long flags;
179
+	int ret;
180
+
181
+	/*
182
+	 * Musn't use RCU; because then the notifier list can
183
+	 * change between the up and down traversal.
184
+	 */
185
+	spin_lock_irqsave(&nh->lock, flags);
186
+	ret = notifier_call_chain_robust(&nh->head, val_up, val_down, v);
187
+	spin_unlock_irqrestore(&nh->lock, flags);
188
+
189
+	return ret;
190
+}
191
+EXPORT_SYMBOL_GPL(atomic_notifier_call_chain_robust);
192
+NOKPROBE_SYMBOL(atomic_notifier_call_chain_robust);
193
+
157194 /**
158
- *	__atomic_notifier_call_chain - Call functions in an atomic notifier chain
195
+ *	atomic_notifier_call_chain - Call functions in an atomic notifier chain
159196  *	@nh: Pointer to head of the atomic notifier chain
160197  *	@val: Value passed unmodified to notifier function
161198  *	@v: Pointer passed unmodified to notifier function
162
- *	@nr_to_call: See the comment for notifier_call_chain.
163
- *	@nr_calls: See the comment for notifier_call_chain.
164199  *
165200  *	Calls each function in a notifier chain in turn.  The functions
166201  *	run in an atomic context, so they must not block.
....@@ -173,24 +208,16 @@
173208  *	Otherwise the return value is the return value
174209  *	of the last notifier function called.
175210  */
176
-int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
177
-				 unsigned long val, void *v,
178
-				 int nr_to_call, int *nr_calls)
211
+int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
212
+			       unsigned long val, void *v)
179213 {
180214 	int ret;
181215 
182216 	rcu_read_lock();
183
-	ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
217
+	ret = notifier_call_chain(&nh->head, val, v, -1, NULL);
184218 	rcu_read_unlock();
185
-	return ret;
186
-}
187
-EXPORT_SYMBOL_GPL(__atomic_notifier_call_chain);
188
-NOKPROBE_SYMBOL(__atomic_notifier_call_chain);
189219 
190
-int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
191
-			       unsigned long val, void *v)
192
-{
193
-	return __atomic_notifier_call_chain(nh, val, v, -1, NULL);
220
+	return ret;
194221 }
195222 EXPORT_SYMBOL_GPL(atomic_notifier_call_chain);
196223 NOKPROBE_SYMBOL(atomic_notifier_call_chain);
....@@ -231,29 +258,6 @@
231258 EXPORT_SYMBOL_GPL(blocking_notifier_chain_register);
232259 
233260 /**
234
- *	blocking_notifier_chain_cond_register - Cond add notifier to a blocking notifier chain
235
- *	@nh: Pointer to head of the blocking notifier chain
236
- *	@n: New entry in notifier chain
237
- *
238
- *	Adds a notifier to a blocking notifier chain, only if not already
239
- *	present in the chain.
240
- *	Must be called in process context.
241
- *
242
- *	Currently always returns zero.
243
- */
244
-int blocking_notifier_chain_cond_register(struct blocking_notifier_head *nh,
245
-		struct notifier_block *n)
246
-{
247
-	int ret;
248
-
249
-	down_write(&nh->rwsem);
250
-	ret = notifier_chain_cond_register(&nh->head, n);
251
-	up_write(&nh->rwsem);
252
-	return ret;
253
-}
254
-EXPORT_SYMBOL_GPL(blocking_notifier_chain_cond_register);
255
-
256
-/**
257261  *	blocking_notifier_chain_unregister - Remove notifier from a blocking notifier chain
258262  *	@nh: Pointer to head of the blocking notifier chain
259263  *	@n: Entry to remove from notifier chain
....@@ -283,13 +287,30 @@
283287 }
284288 EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister);
285289 
290
+int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh,
291
+		unsigned long val_up, unsigned long val_down, void *v)
292
+{
293
+	int ret = NOTIFY_DONE;
294
+
295
+	/*
296
+	 * We check the head outside the lock, but if this access is
297
+	 * racy then it does not matter what the result of the test
298
+	 * is, we re-check the list after having taken the lock anyway:
299
+	 */
300
+	if (rcu_access_pointer(nh->head)) {
301
+		down_read(&nh->rwsem);
302
+		ret = notifier_call_chain_robust(&nh->head, val_up, val_down, v);
303
+		up_read(&nh->rwsem);
304
+	}
305
+	return ret;
306
+}
307
+EXPORT_SYMBOL_GPL(blocking_notifier_call_chain_robust);
308
+
286309 /**
287
- *	__blocking_notifier_call_chain - Call functions in a blocking notifier chain
310
+ *	blocking_notifier_call_chain - Call functions in a blocking notifier chain
288311  *	@nh: Pointer to head of the blocking notifier chain
289312  *	@val: Value passed unmodified to notifier function
290313  *	@v: Pointer passed unmodified to notifier function
291
- *	@nr_to_call: See comment for notifier_call_chain.
292
- *	@nr_calls: See comment for notifier_call_chain.
293314  *
294315  *	Calls each function in a notifier chain in turn.  The functions
295316  *	run in a process context, so they are allowed to block.
....@@ -301,9 +322,8 @@
301322  *	Otherwise the return value is the return value
302323  *	of the last notifier function called.
303324  */
304
-int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
305
-				   unsigned long val, void *v,
306
-				   int nr_to_call, int *nr_calls)
325
+int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
326
+		unsigned long val, void *v)
307327 {
308328 	int ret = NOTIFY_DONE;
309329 
....@@ -314,18 +334,10 @@
314334 	 */
315335 	if (rcu_access_pointer(nh->head)) {
316336 		down_read(&nh->rwsem);
317
-		ret = notifier_call_chain(&nh->head, val, v, nr_to_call,
318
-					nr_calls);
337
+		ret = notifier_call_chain(&nh->head, val, v, -1, NULL);
319338 		up_read(&nh->rwsem);
320339 	}
321340 	return ret;
322
-}
323
-EXPORT_SYMBOL_GPL(__blocking_notifier_call_chain);
324
-
325
-int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
326
-		unsigned long val, void *v)
327
-{
328
-	return __blocking_notifier_call_chain(nh, val, v, -1, NULL);
329341 }
330342 EXPORT_SYMBOL_GPL(blocking_notifier_call_chain);
331343 
....@@ -368,13 +380,18 @@
368380 }
369381 EXPORT_SYMBOL_GPL(raw_notifier_chain_unregister);
370382 
383
+int raw_notifier_call_chain_robust(struct raw_notifier_head *nh,
384
+		unsigned long val_up, unsigned long val_down, void *v)
385
+{
386
+	return notifier_call_chain_robust(&nh->head, val_up, val_down, v);
387
+}
388
+EXPORT_SYMBOL_GPL(raw_notifier_call_chain_robust);
389
+
371390 /**
372
- *	__raw_notifier_call_chain - Call functions in a raw notifier chain
391
+ *	raw_notifier_call_chain - Call functions in a raw notifier chain
373392  *	@nh: Pointer to head of the raw notifier chain
374393  *	@val: Value passed unmodified to notifier function
375394  *	@v: Pointer passed unmodified to notifier function
376
- *	@nr_to_call: See comment for notifier_call_chain.
377
- *	@nr_calls: See comment for notifier_call_chain
378395  *
379396  *	Calls each function in a notifier chain in turn.  The functions
380397  *	run in an undefined context.
....@@ -387,18 +404,10 @@
387404  *	Otherwise the return value is the return value
388405  *	of the last notifier function called.
389406  */
390
-int __raw_notifier_call_chain(struct raw_notifier_head *nh,
391
-			      unsigned long val, void *v,
392
-			      int nr_to_call, int *nr_calls)
393
-{
394
-	return notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
395
-}
396
-EXPORT_SYMBOL_GPL(__raw_notifier_call_chain);
397
-
398407 int raw_notifier_call_chain(struct raw_notifier_head *nh,
399408 		unsigned long val, void *v)
400409 {
401
-	return __raw_notifier_call_chain(nh, val, v, -1, NULL);
410
+	return notifier_call_chain(&nh->head, val, v, -1, NULL);
402411 }
403412 EXPORT_SYMBOL_GPL(raw_notifier_call_chain);
404413 
....@@ -470,12 +479,10 @@
470479 EXPORT_SYMBOL_GPL(srcu_notifier_chain_unregister);
471480 
472481 /**
473
- *	__srcu_notifier_call_chain - Call functions in an SRCU notifier chain
482
+ *	srcu_notifier_call_chain - Call functions in an SRCU notifier chain
474483  *	@nh: Pointer to head of the SRCU notifier chain
475484  *	@val: Value passed unmodified to notifier function
476485  *	@v: Pointer passed unmodified to notifier function
477
- *	@nr_to_call: See comment for notifier_call_chain.
478
- *	@nr_calls: See comment for notifier_call_chain
479486  *
480487  *	Calls each function in a notifier chain in turn.  The functions
481488  *	run in a process context, so they are allowed to block.
....@@ -487,24 +494,16 @@
487494  *	Otherwise the return value is the return value
488495  *	of the last notifier function called.
489496  */
490
-int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
491
-			       unsigned long val, void *v,
492
-			       int nr_to_call, int *nr_calls)
497
+int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
498
+		unsigned long val, void *v)
493499 {
494500 	int ret;
495501 	int idx;
496502 
497503 	idx = srcu_read_lock(&nh->srcu);
498
-	ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
504
+	ret = notifier_call_chain(&nh->head, val, v, -1, NULL);
499505 	srcu_read_unlock(&nh->srcu, idx);
500506 	return ret;
501
-}
502
-EXPORT_SYMBOL_GPL(__srcu_notifier_call_chain);
503
-
504
-int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
505
-		unsigned long val, void *v)
506
-{
507
-	return __srcu_notifier_call_chain(nh, val, v, -1, NULL);
508507 }
509508 EXPORT_SYMBOL_GPL(srcu_notifier_call_chain);
510509 
....@@ -552,7 +551,6 @@
552551 
553552 int register_die_notifier(struct notifier_block *nb)
554553 {
555
-	vmalloc_sync_mappings();
556554 	return atomic_notifier_chain_register(&die_chain, nb);
557555 }
558556 EXPORT_SYMBOL_GPL(register_die_notifier);